Agronomic And Phenotypic Responses To 75 Years Of Recurrent Selection For Yield In The Iowa Stiff Stalk Synthetic Maize Population, Brent Howard Brekke

Graduate Theses and Dissertations

The plant density at which Zea mays L. hybrids achieve maximum grain yield has increased throughout the hybrid era while grain yield on a per plant basis has increased little. Changes in plant traits including grain yield, moisture, test weight, stalk and root lodging, flag leaf angle, anthesis-silking interval(ASI), plant height, tassel branch number, and total number of leaves have been well characterized in comparisons of commercial hybrids representing different eras of hybrid maize production but have yet to be examined in a recurrent selection program.

The objective of this experiment was to determine if direct selection for grain ...

Graduate Theses and Dissertations

The signal recognition particle (SRP) is a ribonucleoprotein complex whose components are highly conserved throughout all three domains of life, where it functions to target proteins to extracytoplasmic locations. In Escherichia coli, the SRP is comprised of a single essential protein (Ffh) in complex with a 4.5S RNA species. To better understand how the structure of Ffh contributes to its function, we have used genetic approaches to isolate and characterize new ffh mutants altered in two distinct domains of the protein. Both domains of interest have been implicated as being important for binding to hydrophobic signal peptides of membrane ...

Faculty Publications and Presentations

The method of electrochemical pretreatment of platinum electrode with the goal of standardizing the initial state of electrode surface and its open-circuit potential (OCP) in the blood and other biological media is proposed. The platinum electrode potential is measured in 0.14 M Na2SO4 aqueous solution, in the blood and blood plasma and serum. By the examples of OCP measured in the blood serum of patients with acute poisoning, acute cerebral pathology and patients treated by the method of hyperbaric oxygenation, it was found that the values of blood serum OCP were different for studied pathological states and healthy people.

Graduate Theses and Dissertations

Iron is an essential element for almost all living organisms. Tissue iron concentration shows natural variations among individuals, because of the influence of both environmental and genetic factors. Body iron, though essential, is also toxic in excess by generating reactive oxygen species. Iron homeostasis, thus, must be maintained systemically by the rate of iron absorption, iron utilization, iron storage and the rate of iron recycling. It is possible that mutations in any of the genes that encode proteins involved in maintaining iron homeostasis have the potential to alter iron load. The effect of single nucleotide polymorphisms (SNPs), a major genetic ...

Var2 Genetic Suppressors, Xiayan Liu

Graduate Theses and Dissertations

The Arabidopsis variegation2 (var2) mutant, displaying a conspicuous green and white sectoring phenotype, is one of the most well-characterized variegation mutants and is the caused by mutations in VAR2, which encodes a subunit of the FtsH metalloprotease complex situated in the chloroplast thylakoid membranes. FtsH proteins mediate a myriad of processes in plants, the most prominent one being the turnover of photosystem II reaction center D1 protein.

The Rodermel lab is interested in using the unique variegation phenotype of var2 mutant as a tool to study the mechanism of variegation and the regulation of chloroplast biogenesis. To this end, our ...

Graduate Theses and Dissertations

A variety of agricultural solutions are being tested to address the recent concern of rising rates of CO2 emissions, one of which is to engineer crops to increase their ability to store atmospheric carbon in soil. By targeting cell wall constituents of crop tissues with longer half-lives, such as lignin, the rate at which fixed CO2 in soil organic matter returns to the atmosphere becomes slowed. Maize is an attractive model organism for this approach, as it is grown worldwide, and has one of the most extensively catalogued plant genomes to date. The objective of this thesis is ...

Ramosa1 In The Development And Evolution Of Inflorescence Architecture In Grasses, Brandi Adell Sigmon

Graduate Theses and Dissertations

Branching architecture of the flower-bearing structures in grasses, known as inflorescences, is a morphological trait that is subject to natural and artificial selection since it affects both reproduction and grain yield. Genes underlying this trait are sought to explain the molecular basis underlying the phenotypic diversity of these structures. The ramosa1 (ra1) gene encodes a transcription factor that controls branching architecture in maize inflorescences (tassel and ear). Reduced ra1 activity in maize produces ears with crooked rows of kernels due to the generation of extra spikelets, a phenotype that may have been selected on during the derivation of modern maize ...

Graduate Theses and Dissertations

The objective was to quantify the naturally occurring free L-Carnitine (FC), acylated (AC), and total carnitine (TC) in skeletal muscle of Angus beef cattle. These data then were correlated to the yield grade (YG) and marbling scores (MS) of the same samples of longissmus dorsi muscles at 12th rib were collected from 1085 purebred Angus bulls, steers, and heifers from Iowa and California and used to quantify different the forms of carnitine. The spectrophotometric and enzymatic quantification of the different carnitines demonstrated that concentration of FC ranged from 2.12 to 6.32 ymol/g of beef and averaged 3 ...

Graduate Theses and Dissertations

As the major physiological inhibitor of plasminogen activator (PA), the type I plasminogen activator inhibitor (PAI-1) is important for controlling blood clotting and tissue remodeling events such as those that involve cell migration. The changing needs for protease activity under various physiological conditions necessitates a tight cellular control of gene expression to enable rapid changes in the levels of PAI-1 and PA activity. Cooperation between epidermal growth factor (EGF) and transforming growth factor-β (TGF-β) dramatically increase PAI-1 protein level. In this study, we found activators of tyrosine kinase (EGF, FGF, IGF-I and TNF α) or an activator of PKC (PMA ...

The Regulation Of Hypoxia-Inducible Factor (Hif-1) And The Role Of Hif-1 In C. Elegans Longevity, Zhiwei Zhai

Graduate Theses and Dissertations

Oxygen is one of the most abundant elements on the earth. It is the final electron receptor of aerobic respiration, which is an essential energy generation process in living creatures. Oxygen homeostasis is crucial for the survival and function of cells (Semenza, 2000). In animals, the oxygen levels exposed to each individual cell are systemically controlled by the respiration system and circulatory system.

Hypoxia-inducible factor (HIF) transcription factors play key roles in oxygen homeostasis from invertebrate C. elegans to human beings. HIF is a heterodimeric transcription factor, consisting of an alpha subunit that is regulated by oxygen and a beta ...

Graduate Theses and Dissertations

A series of experiments was conducted to eliminate activity of SBA. Deglycosylation decreased activity of SBA by 21%, but not as much as denaturation (23-53%). Single enzymes did not hydrolyze native SBA, but hydrolyzed heat- or organic solutes-denatured SBA. Even after hydrolysis, activity of SBA still was not fully eliminated (44-62% residual). A combination of multiple enzymes with thermolysin fully deactivated heat- or organic solutes-treated SBA. Tea polyphenols, metal ions, chelating agents were also tested and had no significant effect on deactivating SBA. N-acetyl-galactosamine (GalNAc)-agrose beads specifically removed SBA from a protein mixture, but not fully and activity of ...

Environmental Support And Physical Education Teacher Self-Efficacy: A Test Of Social Cognitive Theory, Matthew Buns

Graduate Theses and Dissertations

There is a need for sound self-efficacy measures in education that are based on Social Cognitive Theory. Physical education benefits public health by addressing physical inactivity and obesity. The purpose of this study was to develop and test a standards-based training program and virtual blog on self-efficacy. Participants were 60 physical education teachers recruited from 16 school districts. Three self-efficacy scales were administered at the beginning of a workshop and after a six-week collaborative blog. The major finding is that the intervention enhanced self-efficacy to a much greater extent than the control group. The average experimental group effect size for ...

Graduate Theses and Dissertations

Studies on climate change have shown an increase in not only the average global surface temperature but also an increase in extreme weather events. One such extreme weather event is the occurrence of winter temperature fluctuations, which can induce loss of cold acclimation. Sudden temperature fluctuations have occurred in the United States in the early spring of 2007 and the late winter of 2009. Both events caused significant freezing damage to plants. However, plants that were able to maintain a portion of their original freezing tolerance, by a process called deacclimation resistance, did not suffer significant damage.

Graduate Theses and Dissertations

Fusarium virguliforme (Fv) is the causal organism of the sudden death syndrome (SDS) in soybean (Glycine max [L.] Merr). The estimated average annual soybean yield loss from this disease is valued at about 300 million dollars. F. virguliforme is a soil borne fungus, which attacks soybean roots and causes root rot as well as chlorosis and necrosis in foliar tissues. The pathogen has never been isolated from the diseased foliar tissues. It was therefore hypothesized that a toxin(s) is involved in the development of the disease.

Ophiostomatales Isolated From Two European Bark Beetles, Hylurgus Ligniperda And Orthotomicus Erosus, In California, Sujin Kim

Graduate Theses and Dissertations

Two European pine-infesting bark beetles, Hylurgus ligniperda and Orthotomicus erosus, were first detected in July 2003 in Los Angeles, California and in May 2004 in the Central Valley of California, respectively. These bark beetles (Coleoptera: Curculionidae: Scolytinae) are common vectors of fungi in the Ophiostomatales, some of which are tree pathogens or causal agents of blue stain of conifer sapwood. Ophiostomatales were isolated on a cycloheximide-amended medium, which is semi-selective for the growth of Ophiostoma and related genera. In total, eight identified species and seven unidentified species of Ophiostomatales were isolated from 118 adults of H. ligniperda collected from infested ...

Brassinosteroid Regulation Of Plant Height In Maize, Gokhan Kir

Graduate Theses and Dissertations

Brassinosteroids (BRs) are a type of phytohormone that has important roles in plant development. Even though they are well studied in model species, their role in maize development is poorly understood. To address this issue, two approaches were undertaken. Since it was shown mutations in BRs biosynthesis or signaling cause dwarfism in other plants, novel maize dwarf mutants were screened to see if they are related to the BRs. Phenotypic and genetic characterization led to the identification and genetic mapping of at least 2 likely candidates. The results of this work are presented in Chapter 2. In the second part ...

Graduate Theses and Dissertations

The western corn rootworm Diabrotica virgifera virgifera LeConte (Coleoptera: Chrysomelidae) is a major soil-borne pest of corn Zea mays L. in both the United States and Europe, where larval feeding on corn roots can cause severe economic losses. Two factors that can affect survival of larval D. v. virgifera are natural populations of soil-dwelling entomopathogens and transgenic corn, Zea mays L., expressing genes from Bacillus thuringiensis Berliner (Bt). During the fall of 2008 and 2009, we measured incidence of entomopathogenic fungi and nematodes in corn fields that displayed a high abundance of D. v. virgifera by exposing three insect species ...

Medial Longitudinal Arch Mechanics Before And After A Prolonged Run, Elizabeth Rose Hageman

Graduate Theses and Dissertations

Collapse and reformation of the medial longitudinal arch during gait is controlled passively and actively. If either tissue group fatigues over the duration of a run, the change in arch mechanics may increase risk of running injuries. However, a 3-dimensional kinematic analysis of the medial longitudinal arch after a prolonged run has not been performed. Additionally, rarely has arch collapse been quantified for walking and running in the same study. PURPOSE: To compare arch mechanics before and after a 45 minute run and to compare walking and running arch deformation. METHODS: Thirty runners performed barefoot walking and running trials before ...

Graduate Theses and Dissertations

The SAGA family of coactivators is a group of highly conserved histone acetyltransferases that is essential for transcription of genes participating in stress adaptation and developemental processes. Misregulation of SAGA function can lead to developmental diseases and cancer. One important function of SAGA in regulating gene expression is to acetylate nucleosomes at both gene promoters and coding regions. To understand the molecular mechanism of nucleosome acetylation, much work has been done using recombinant Gcn5, the catalytic subunit of SAGA, and histone proteins or peptides. However, little is known about how histones are acetylated by full SAGA complex in the context ...

Graduate Theses and Dissertations

Soybean [Glycine max (L.) Merr.] oils with high-oleate (HO) or low linolenate (LL) concentrations have greater oxidative stability and longer shelf-life than conventional soybean oil. Soybean lines with the transgenic event DP-305423-1 produce a high-oleate oil and those with the fan1(C1640) and fan3(RG10) alleles produce a low-linolenate oil. The objective of this study was to evaluate the agronomic and seed traits of high-oleate/low-linolenate (HOLL) lines, high-oleate/normal-linolenate (HONL) lines, and normal-oleate/normal-linolenate (NONL) lines selected from four single-cross populations formed by crossing a HOLL parent homozygous for the transgene and the two fan alleles to four conventional ...